1. Field of the Invention
The present disclosure relates to an array substrate for a liquid crystal display (LCD) device, and more particularly, to an array substrate for an LCD device having a repair pattern.
2. Discussion of the Related Art
The conventional LCD devices use an optical anisotropic property and polarization properties of liquid crystal molecules to display images. The liquid crystal molecules have orientation characteristics of arrangement resulting from their long, thin shape. Thus, an arrangement direction of the liquid crystal molecules can be controlled by applying an electrical field to them. Accordingly, when the electric field is applied to them, polarization properties of light are changed according to the arrangement of the liquid crystal molecules such that the LCD devices display images.
The LCD device includes a first substrate, a second substrate, and a liquid crystal layer interposed therebetween. A common electrode and a pixel electrode are respectively formed on the first and second substrates. The first and second substrates may be referred to as a color substrate and an array substrate, respectively. The liquid crystal layer is driven by a vertical electric field induced between the common and pixel electrodes. LCD devices typically have excellent transmittance and aperture ratios.
Among the known types of LCD devices, active matrix LCD (AM-LCD) devices that have thin film transistors (TFTs) arranged in a matrix form are the subject of significant research and development because of their high resolution and superior ability in displaying moving images.
FIG. 1 is an exploded perspective view of a conventional liquid crystal panel of an LCD device. As shown in FIG. 1, the liquid crystal panel includes an array substrate 10, a color filter substrate 80, and a liquid crystal layer 70. The array substrate 10 and the color filter substrate 80 face each other. The liquid crystal layer 70 is interposed therebetween.
The array substrate 10 includes a first substrate 12, a gate line 13, a data line 30, a thin film transistor (TFT) Tr, and a pixel electrode 60. The gate and data lines 13 and 30 are formed on the first substrate 12 and cross each other to define a pixel region P. The TFT Tr is formed at a crossing portion of the gate and data lines 13 and 30. The pixel electrode 60 is formed in the pixel region P and connected to the TFT Tr.
The color filter substrate 80 includes a second substrate 82, a black matrix 85, a color filter layer 89, and a common electrode 92. The black matrix 85 is formed on the second substrate 82 and has a lattice shape. The black matrix 85 corresponds to a non-display region of the first substrate 12. The non-display region of the first substrate 12 also includes the gate and data lines 13 and 30 and the TFT Tr. The color filter layer 89 corresponds to the pixel region “P” and has one of red (R), green (G), and blue (B) colors 89a, 89b, and 89c. The common electrode 92 is formed on the black matrix 85 and the color filter layer 89. The common electrode 92 generates an electric field with the pixel electrode 60 such that the liquid crystal layer 70 is driven by the electric field.
Though not shown, first and second polarization plates may be formed on an outer surface of the first and second substrates 12 and 82. The first and second polarization plates respectively have first and second optical axes, and light parallel to each of the first and second optical axes can be passed through the first and second polarization plates, respectively. Moreover, a backlight assembly is formed on a rear side of the first substrate 12 to apply light into the liquid crystal panel.
FIG. 2 is a plane view showing an array substrate for an LCD device according to the related art. As shown in FIG. 2, a plurality of gate lines 13 and a plurality of data lines 30 are formed on a first substrate 12. The plurality of gate lines 13 and the plurality of data lines 30 cross each other such that a plurality of pixel regions P are defined. A gate pad (not shown) is formed at an end of each gate line 13. Each gate line 13 is connected to a gate driving circuit (not shown) via the gate pad. A data pad (not shown) is formed at an end of each data line 30. Each data line 30 is connected to a data driving circuit (not shown) via the data pad.
A thin film transistor (TFT) Tr is formed in each pixel region P. The TFT Tr is connected to the gate and data lines 13 and 30. A gate electrode 15, a semiconductor layer 23, a source electrode 33 and a drain electrode 36 constitute the TFT Tr. The gate electrode 15 is connected to the gate line 13, and the source electrode 33 is connected to the data line 30. The drain electrode 36 is spaced apart from the source electrode 33. A pixel electrode 60 is formed in each pixel region P. The pixel electrode 60 is connected to the drain electrode 36 through a drain contact hole 47. Moreover, a storage capacitor StgC is formed over the gate line 13. A storage pattern 15 overlaps the gate line 13 and is connected to the pixel electrode 60 through a storage contact hole 49. The overlapped portion of the gate line 13 functions as a first electrode, and the storage pattern 15 functions as a second electrode. An insulating layer (not shown) interposed between the overlapped portion of the gate line 13 and the storage pattern 15 functions as a dielectric material. The first electrode, the second electrode, and the insulating layer constitute the storage capacitor StgC.
The array substrate is fabricated through complicated processes such that defects may arise during the processes. Static electricity may be generated during the process. Moreover, the TFT may be deteriorate due to impurities such that the TFT does not have its desired functions. In this case, the defects may be repaired by disconnecting the pixel electrode 60 and the drain electrode 36 in the pixel region P. As a result, the LCD device displays only white color in a normally white mode and black color in a normally black mode in the pixel region P having the pixel electrode 60 disconnected from the drain electrode 36. In the normally white mode, white color is displayed in the pixel region P in which a signal is not applied. In contrast, in the normally black mode, black color is displayed in the pixel region in which a signal is not applied.
The LCD device may have tens of thousands to tens of millions of the pixel regions P depending on size or resolution of the liquid crystal panel. If the LCD devices are considered acceptable for sale only when all pixel regions P function well, production yield becomes too low. Accordingly, although some pixel regions P do not display desired images, the LCD devices are treated as acceptable for sale and considered to be without defect. A method of repairing by disconnecting the pixel electrode 60 from the drain electrode 36 in some pixel regions P may not affect quality of the displaying images.
However, there are some problems. When the LCD device has the normally black mode and displays bright images, the repaired pixel region P in which black color is normally displayed may be conspicuous. In contrast, when the LCD device has the normally white mode and displays dark images, the repaired pixel region in which white color is normally displayed may be conspicuous.